Rubber modified olefinic nitrile-vinyl aromatic-maleimide interpolymers

ABSTRACT

Interpolymers having high impact strength, high softening temperature and other excellent properties result from the polymerization of an olefinic nitrile such as acrylonitrile, a vinyl aromatic monomer such as styrene, and maleimide in the presence of a conjugated diolefin elastomer.

United States Patent [1'91 Uebele et al. MSlMarch 20, 1973 [54] RUBBERMODIFIED OLEFINIC [56] References Cited NITRILE-VINYL AROMATIC- IMALEIMIDE INTERPOLYMERS UNITED STATES PATENTS e r 5 I 3,322,853 5/1967Trementozzi ..260/879 [75] Inventors: Curtis E. Uebele, Bedford; Russell3,549,725 12/1970 Rose ..260/78 UA K. Griffith, Chagrin Falls; IrvingRosen, Painesville, all of Ohio 7 FOREIGN PATENTS OR APPLICATIONS V Q1,185,544 3/1970 Great Britain .....26O/78 UC [73] Assignee: ThevStandard Oil Company, Cleveland, Ohio Primary Examiner-James A. Seidleck1 Filed; Sept 22 1970 Attorney-John F. Jones and Sherman .l. Kemmer[2'1] Appl. No.: 74,290 I [57] ABSTRACT Interpolymers having high impactstrength, high softening temperature and other excellent properties [52](126M880 result from the polymerization of an olefinic nitrile such asacrylonitrile, a vinyl aromatic monomer such 08! 19/08 s g g fi asstyrene, and maleimide in the presence of a conjugated diolefinelastomer.

8 Claims, 1 Drawing Figure RUBBER MODIFIED OLEFINIC NITRILE-VINYLAROMATlC-MALEIMIDE INTERPOLYMERS The present invention is concerned withhigh impact strength interpolymers of an olefinic nitrile monomer, avinyl aromatic monomer and maleimide, and more particularly pertains tointerpolymers having high impact strength, high softening temperatureand other good physical properties resulting from the polymerization ofan olefinic nitrile such as acrylonitrile, a vinyl aromatic monomer suchas styrene, and maleimide in the presence of a conjugated diolefinelastomer.

The polymers of this invention have markedly superior physicalproperties in relationship to most prior art rubber-reinforced polymers.

The olefinically unsaturated nitrile monomers useful in the presentinvention are those having the structure CHEG CN it wherein R representshydrogen, a lower alkyl group and a halogen, and more preferably whereinR. is hydrogen or an alkyl'group having from one to four carbon atoms.Preferred from this classfor the purpose of this invention areacrylonitrile and methacrylonitrile and most preferred is acrylonitrile.

The vinyl aromatic monomers included herein'are styrene-and the alkylandhalo-substituted styrenes. The alkyl-substituted styrenes include thenuclear and side chain alkyl-substituted styrenes such as alphamethylstyrene, alpha-ethyl styrene, the vinyl toluenes, the vinyl xylenes, theisopropyl styrenes, the t-butyl styrenes such as o-, mand p-t-butylstyrenes, mand p-methyl, alpha-methyl styrenes, and the like, andmixtures of the same. The preferred vinyl aromatic monomer is styrene.Halogenated vinyl aromatic monomers useful in this invention include thenuclear halogenated vinyl aromatic monomers, such as themonochlorostyrenes, the dichlorostyrenes, the trichlorostyrenes, thetetrachlorostyrenes, pentachlorostyrene, the monobromostyrenes, thedibromostyrenes, the tribromostyrenes, the tetrabromostyrenes, thepentabromostyrenes, the

chlorinated alpha-methyl styrenes, the brominated alpha-methyl styrenes,the chlorinated vinyl toluenes, the brominated vinyl toluenes, thechlorinated vinyl xylenes, the brominated vinyl xylenes, and the like.Mostpreferred of the halo vinyl aromatic monomers are the nuclearmonochlorinated styrenes such as 2- chlorostyrene, 3-chlorostyrene,4-chlorostyrene, and mixtures of two or more thereof.

Conjugated diolefin elastomers useful in the present invention includerubbery homopolymers and copolymers of conjugated dienes having fromfour to six carbon atoms. Such conjugated dienes include butadien'e l,3,isoprene, chloroprene, piperylene, cyanoprene, and the like; and one ormore of these dienes can also be copolymerized with one or morecomonomers including acrylonitrile, methacrylonitrile, styrene,alpha-methyl styrene, ethyl acrylate, and the likez-Most preferredconjugated dienes are butadiene- 1,3 and isoprene and most preferredcomonomers for the elastomer are acrylonitrile, methacrylonitrile andstyrene; The diene elastomers useful in this invention should contain50. percent by weight or more of polymerized conjugated diene monomer.

Maleimide useful in this invention conforms to the structure and is alsosometimes called maleic imide and maleinimide.

The interpolymers most useful in the present invention are those whichresult from the polymerization of parts by weight of nitrile, styreneand maleimide mixture in the presence of from about one to 25 parts byweight of the conjugated diolefin elastomer.

In the accompanying drawing, FIG. 1 illustrates the unobvioussuperiority of maleimide when used in the polymers of the instantinvention as compared with various N-substituted maleimides many ofwhich have been disclosed in the prior art. In FIG. 1 the ASTM heatdistortion temperatures (HDT) for several polymers are plotted versusthe weight percent of the particular maleimide in the polymerizationmonomer feed. The polymers given in FIG. 1 are all interpolymers ofstyrene, acrylonitrile, the maleimide shown and a polybutadiene asdescribed in Examples 2-7 below.

The molar ratio of vinyl aromatic monomer to olefinic nitrile monomercan vary from 0.5 to 10 and correspondingly the molar ratio of maleimideto olefinic nitrile can vary from 0.2 to 2.5.

Copolymerization of the olefinic nitrile, vinyl aromatic and maleimidemonomers in the presence of the rubber can be carried out by heating.them in mass, in an inert solvent, in emulsion, or while dispersed .asdroplets in an inert medium, i.e., in suspension in water, and at atemperature in the range of about 0C or below to about 100C or above,and at atmospheric, subatmospheric or superatmospheric pressure, usuallyin the presence of a polymerization initiator or catalyst and in thesubstantial absence of oxygen. Preferred because of convenience inhandling and recovery of product is an aqueous emulsion or suspensionprocess in which the monomers are copolymerized in the presence of anaqueous emulsion or suspension of the preformed rubber.

' Polymerization initiators or catalysts which may be used in theinterpolymerization of the olefinically unsaturated nitrile, vinylaromatic monomer and maleimide in the presence of the rubber include theper-acid catalysts such as persulfuric acid, peracetic acid andperphthalic acid; the per-salt catalysts such as potassium persulfate;the peroxide catalysts such as hydrogen peroxide, benzoyl peroxide,chlorobenzoyl peroxide, bromobenzoyl peroxide, naphthoyl peroxide,acetyl peroxide, benzoyl acetyl peroxide, lauryl peroxide, succinylperoxide, di-t-butyl peroxide, dicumyl peroxide,

The polymerization can be most advantageously carried out at atemperature in the range of from about C to 100C in the substantialabsence of molecular oxygen.

The polymerization can be carried to completion without substantialinterruption or it may be stopped at any point short of completion.Unreacted polymerizable material may be separated from the polymer byany suitable method such as filtration, extraction, distillation, andthe like. The polymerization may be accomplished in any suitable type ofapparatus and may be conducted in a batch, semi-continuous or continuousmanner.

A particularly preferred method for the interpolymerization comprises anaqueous emulsion polymerization process wherein an aqueous emulsion ofmonomer is polymerized in admixture with an aqueous latex of theelastomer.

Emulsifying agents which may be used in the aqueous emulsionpolymerization process include the soaps such as sodium and potassiummyristate, laurate, palmitate, oleate, stearate, resinate andhydroabietate; alkali metal alkyl or alkylene sulfonates such as sodiumand potassium lauryl sulfate, cetyl sulfate, oleyl sulfonate, stearylsulfonate, sulfonated castor oil, as well as ammonium salts thereof;salts of higher amines such as lauryl amine hydrochloride and stearylamine hydrobromide; and higher molecular weight materials such as sodiumpolyacrylate, methyl cellulose, polyvinyl pyrrolidone, etc.

Suitable molecular weight modifiers, such as the alkyl and arylmercaptans including n-dodecyl mercaptan, t-dodecyl mercaptan, and thelike may be employed in the polymerization in amounts of from about 0.01percent to about 1.0 percent by weight based on the total weight ofmonomer material in polymerization reaction.

The product of the aqueous emulsion polymerization is usually a latex.The interpolymers may be recovered from the latex by any suitable meanssuch as by coagulation with electrolytes or solvents, by freezing, andthe like.

Other modifiers, including plasticizers, stabilizers, lubricants, dyes,pigments, and fillers, may be added during the polymerization processprovided they do not adversely affect the ingredients of the reactionmixture. Otherwise, these modifiers may be added following thepolymerization. Examples of other modifying agents and pigments whichmay be added are wood flour, wood fibers, paper dust, clay, glass wool,glass fibers, mica, granite dust, silk flock, cotton flock, steel wool,cloth, sand, carbon black, titanium dioxide, zinc oxide, lead oxide,chrome yellow, gums, oils, waxes, and the like.

Other compounding ingredients, such as extenders, stabilizers, colors,and the like, may be used in preparing the compositions of thisinvention, as is well known in the art, so long as the balance betweenimpact strength, flexural strength, tensile strength, processability,heat distortion temperature, and the like, is not affected to such adegree that the composition is no longer useful as a tough, rigidthermoplastic product.

The thermoplastic resins resulting from this invention possess high heatdistortion temperatures, high tensile strengths, high flexuralstrengths, a high degree of hardness, high impact strengths, and lowcreep.

the

The compositions of this invention have excellent processingcharacteristics and they may be extruded, calendered, molded, drawn,embossed, machined, and otherwise treated to form useful, rigid,shock-resistant products and articles which have an excellent balance ofgood chemical, physical and electrical properties.

The thermoplastic resin compositions of this invention can be used tomake all sorts of useful extruded or molded (injection or compression)shapes such as sheets, rods, tubes, and the like, as well as milled orcalendered sheets or the like which can also be afterformed by Vacuumdrawing or similar operations. They may be expanded by incorporatingblowing agents and heating. Expanded and unexpanded sheets may belaminated. The compositions of this invention may be substituted togreat advantage for the usual rubber of plastic compositions, or evenfor metals, wood or other materials, in many applications wheretoughness and resistance to creep and distortion at elevatedtemperatures are required. The resins are particularly useful in theproduction of articles and implements which must be subjected torelatively high heat for relatively long times such as medicalinstruments and the like. Thus, the present compositions may be used tofabricate parts for machines such as gears and cams; parts for textilemachinery such as bobbins, shuttles, pickers, etc.; containers andpipes, especially for chemical and like operations, where resistance tocorrosive substances is desired as in filter press plates and tumblingbarrels for plating operations, electrical parts such as terminalblocks, telephones, and protective casings for cable joints; as well astote boxes and trays, luggage, radio cabinets, furniture, phonographrecords, signs, small boat hulls and decks, paneling or covering forwalls and surfaces of buildings, railroad cars or ships; protectivearmor including body armor; automobile parts such as head liners,steering wheels, door panels and seat parts; roller skate wheels,protective helmets, packaging material for foods, drugs and cosmetics,printing plates, tools, die cutting blocks, washing machine parts suchas covers, baskets, bearings and impellers; and numerous other articlesas will be evident to those skilled in the art. The thermoplasticresinous compositions of this invention may be laminated or otherwisereinforced as with fibers, fabrics or wire mesh, if desired, in makinguseful articles therefrom, although usually the strength of thesematerials will be adequate without reinforcement.

ln the following examples which will further illustrate this invention,the amounts of ingredients are given in parts by weight unless otherwiseindicated.

Example 1 A. A polybutadiene rubber latex prepared by the emulsionpolymerization of butadiene-l,3 at 122F using a resin fatty acid soapemulsifier having a pH between 9.5-l l and a total solids content of57.5-61 percent by weight was employed as the rubber latex in thisexample.

B. A mixture of styrene, acrylonitrile and maleimide monomers waspolymerized in the presence of the polybutadiene latex described in Aabove. The following ingredients were used in the polymerizationmixture:

Parts Styrene 67.1

Maleimide 15.7 Acrylonitrile 17.2 Rubber Latex A above 15.0 (based on 7rubber solids) Water 700 Sodium Lauryl Sulfate 3.5 Benzoyl Peroxide 0.58

The polymerization was carried out in a polymerization reactor at about70C in a nitrogen atmosphere and with stirring. The polymerizationreaction was carried out for about 22 hours.

At the end of the polymerization reaction the resulting resin from thepolymer latex was coagulated by adding the latex to an excess of boilingisopropanol which contained a small amount of a saturated aqueoussolution of AI (SO The 'coagulated resin was allowed to settle, part ofthe supernatant liquid was discarded, ice was added to the resin slurryto harden the particles, and the polymer was isolatedby filtration. Thepolymer was then vacuum dried at 50 to 90C. A 90 percent yield wasobtained.

Compression molded bars were prepared from the resinous polymer byplacinglO grams of resin in a k X 5 inch steel mold and compressing thepolymer at a temperature of 200 to 220C under a hydraulic ram pressureof 8 to 10 tons for 6-8 minutes. The sample was then cooled to near roomtemperature under a ram pressure of 6 to 10 tons, the pressure wasreleased, and the resulting molded bars were released from the mold andtrimmed of flash material. The bars were subjected to physical testingand were found to have the following properties: ASTM Test No. 648 heatdistortion temperature (264 psi) 133C, Flexural strength 10,900 psi,

Flexural modulus 289,000 psi, Tensile strength 6,390 psi, and notchedIzod impact strength 1.28 foot pounds per inch of notch.

Example 2 A series of polymers were prepared according to the procedureof Example 1 in which the styrenezacrylonitrile ratio and amount ofrubber were maintained but the amount of maleimide in the polymerizationfeed was varied. The effect of this variation of maleimide in thepolymer on the ASTM heat distortion temperature (I-IDT) of the resultingresin is shown in FIG. 1 in the accompanying drawing. In FIG. 1 Weightin Feed means weight percent of the designated monomer in the initialpolymerization recipe in relation to the weight of the other monomersand excluding the weight of the rubber employed in the polymerizationrecipe.

EXAMPLE 3 Example 2 was repeated with the exception that Nphenylmaleimide was substituted for maleimide. The ASTM heat distortiontemperature for these resins, which are outside the scope of the presentinvention, are given in FIG. 1. It was also observed that the yield ofinterpolymers prepared with N-phenylmaleimid'e according to this examplewere always considerably lower than for those prepared with maleimide,and the maleimide interpolymers were on the order of 1,000 times moreresistant to hydrolysis than were the corresponding N-phenylmaleimideinterpolymers.

EXAMPLE 4 Example 2 was repeated using N-cyclohexylmaleimide in place ofmaleimide. The effect of the amount of N-cyclohexylmaleimide on the ASTMheat distortion temperature of the resulting resins, which are outsidethe scope of the present invention, is given in FIG. 1.

EXAMPLE M5 Example 2 was repeated except that N-methylmaleimide wassubstituted for maleimide. The effect of the N-methylmaleimide level inthe resins, which are outside the scope of the present invention, on theASTM heat distortion temperature is shown in FIG. 1.

EXAMPLE 6 Example 2 was repeated except that N-ethylmaleimide wassubstituted for maleimide. The effect of the level of N-ethylmaleimideon the heat distortion temperature for these resins, which are outsidethe scope o the present invention, is given in FIG. 1. 1

EXAMPLE 7 Example 2 was repeated except that N-butylrnaleimide wassubstituted for maleimide. The effect of the N-butylmaleimide level inthe resins, which are outside the scope of the present invention, on theASTM heat distortion temperature is given in FIG. 1.

EXAMPLE 8 EXAMPLE 9 Example 1 was repeated using a molar ratio ofstyrone:maleimidezacrylonitrile of 1:0.5 :2 (40.3:19:40.7 parts byweight), respectively. The final resin was compression molded into testbars and was found to have the following physical properties: ASTM heatdistortion temperature 127C, Flexural strength 6,630 psi, Flexuralmodulus 176,000 psi, Tensile strength 3,940 psi and notched Izod impactstrength 2.18 foot pounds per inch of notch.

EXAMPLE 10 Example I was repeated using a rubbery butadienestyrene (-25)copolymer latex with results similar to those reported in Example 1.

We claim:

1. The resinous polymer resulting from the polymerization of parts byweight of A. an olefinically unsaturated nitrile monomer having thestructure wherein R represents hydrogen, a lower alkyl group and ahalogen, and

B. from 0.5 to 10 moles per mole of (A) of a vinyl aromatic monomer, and

C. from 0.2 to 25 moles per mole of (A) of maleimide,

in the presence of from about one to 25 parts by weight of a conjugateddiolefin elastomer composed of 50 percent or more by weight of apolymerized conjugated diene monomer selected from the group consistingof butadiene-1,3, isoprene, chloroprene, piperylene and cyanoprene andup to 50 percent by weight of one or more comonomers selected from thegroup consisting of acrylonitrile, methacrylonitrile, styrene,alphamethyl styrene, and ethyl acrylate.

2. The composition of claim 1 wherein the nitrile monomer isacrylonitrile.

3. The composition of claim 2 wherein the vinyl aromatic monomer isstyrene.

4. The composition of claim 3 wherein the conjugated diolefin elastomeris polybutadiene.

5. The process comprising polymerizing with a polymerization initiatorin an aqueous emulsion with an emulsifying agent in the substantialabsence of molecular oxygen at a temperature in the range of about C to100C a mixture of 100 parts by weight of A. an olefinically unsaturatednitrile monomer having the structure wherein R represents hydrogen, alower alkyl group and a halogen, and B. from 0.5 to 10 moles per mole of(A) of a vinyl aromatic monomer, and C. from 0.2 to 2.5 moles per moleof (A) of maleimide, and from about 1 to 25 parts by weight of aconjugated diolefin elastomer composed of 50 percent or more by weightof a polymerized conjugated diene monomer selected from the groupconsisting of'butadiene-LS, isoprene, chloroprene, piperylene andcyanoprene and up to 50 percent by weight of one or more comonomersselected from the group consisting of acrylonitrile, methacrylonitrile,styrene, alpha!-methyl styrene, and ethyl acrylate.

6. The process of claim 5 wherein the nitrile monomer is acrylonitrile.

7. The process of claim 6 wherein the vinyl aromatic monomer is styrene.

8. The process of claim 7 wherein the conjugated diolefin elastomer ispolybutadiene.

2. The composition of claim 1 wherein the nitrile monomer isacrylonitrile.
 3. The composition of claim 2 wherein the vinyl aromaticmonomer is styrene.
 4. The composition of claim 3 wherein the conjugateddiolefin elastomer is polybutadiene.
 5. The process comprisingpolymerizing with a polymerization initiator in an aqueous emulsion withan emulsifying agent in the substantial absence of molecular oxygen at atemperature in the range of about 0*C to 100*C a mixture of 100 parts byweight of A. an olefinically unsaturated nitrile monomer having thestructure wherein R represents hydrogen, a lower alkyl group and ahalogen, and B. from 0.5 to 10 moles per mole of (A) of a vinyl aromaticmonomer, and C. from 0.2 to 2.5 moles per mole of (A) of maleimide, andfrom about 1 to 25 parts by weight of a conjugated diolefin elastomercomposed of 50 percent or more by weight of a polymerized conjugateddiene monomer selected from the group consisting of butadiene-1,3,isoprene, chloroprene, piperylene and cyanoprene and up to 50 percent byweight of one or more comonomers selected from the group consisting ofacrylonitrile, methacrylonitrile, styrene, alpha--methyl styrene, andethyl acrylate.
 6. The process of claim 5 wherein the nitrile monomer isacrylonitrile.
 7. The process of claim 6 wherein the vinyl aromaticmonomer is styrene.
 8. The process of claim 7 wherein the conjugateddiolefin elastomer is polybutadiene.